I just installed a HR20 and just purchased a Harmony 890 remote. Please help me with the following questions 1) Do I need a external RF Antenna for my HR20? DirecTV says I need the antenna, but I have also read that the HR20 has it built in. I don't see a place on the back of the HR20 for the antenna. 2) If I need a external Antenna, can I just buy the antenna? DirecTV does not list just the antenna? Thanks!!!